MH370 search moves closer to Aust

THE search for missing Malaysia Airlines flight MH370 in the southern Indian Ocean has moved closer to Australia, with experts halving the area of water where the plane might be found.

And while efforts so far have failed to find signs of the jet, search co-ordinators at the Australian Maritime Safety Authority remain confident.

"With a smaller area closer to Perth and more aircraft ... I hope we will do better tomorrow," the authority's head of emergency response John Young said on Wednesday.

Four military aircraft from Australia, New Zealand and the United States on Wednesday combed a 300,000 square kilometre area, 2300km southwest of Perth, where conditions were clear enough to spot marine life.

"The search area has been significantly refined," Mr Young said.

The previous search zone of 600,000 square kilometres, 3200km from Perth, have been reduced following more detailed analysis from the US National Transportation Safety Board.

The new calculations are based on MH370's fuel reserves.

Four ships have passed through the area with another due on Thursday, when up to five aircraft will again fly over.

Flight MH370 - carrying 239 people including six Australians - disappeared during a March 8 service bound for Beijing.

"We still have grave fears for the safety of anyone who might have managed to escape the aircraft in the southern (Indian) Ocean," Mr Young said.

"It remains a big area, it's still very hard to search 300,000 square kilometres ... still almost a third bigger than the state of Victoria."